The invention relates to a unidirectional clutch mechanism for electric motors that becomes operational (engages) in one axial and one angular shaft direction.
The purpose of this mechanism is to prevent a worm and gear in a motor from being back driven in the event that an external torque is applied at the output end of a gear arrangement. Currently this function is achieved by decreasing the gearing efficiency; however, the negative effect is that the overall system efficiency is decreased as well, possibly requiring a larger motor. By selectively having the ability to lock the system worm and gear, the gearing efficiency can be optimized to a higher level without major concerns for back drive.
Current systems with similar functionality are based on the overrunning clutch drive configuration with an added taper to the shaft, so axial and radial engagements are selectively accomplished. These configurations are comprised of numerous small components that add cost to the system.
Thus, there is a need to provide a clutch mechanism that locks the system worm and gear and has fewer parts than conventional assemblies.
An object of the present invention is to fulfill the need referred to above. In accordance with the principles of the present invention, this objective is obtained by providing a clutch mechanism of a motor. The motor has a shaft, a worm associated with the shaft, a gear engaged by the worm, and a friction surface. The clutch mechanism includes a pressure plate mounted for movement with respect to the shaft toward and away from the friction surface. A spring is constructed and arranged to bias the pressure plate towards the friction surface. A stop is constructed and arranged to limit movement of the pressure plate in a direction away from the friction surface. Whereby, under a back drive condition of the motor when the motor is not energized and the gear is moved by an externally applied torque causing an axial force to be exerted on the worm inducing an axial and an angular movement to the shaft, the pressure plate is constructed and arranged to move towards and engage the friction surface thereby impeding rotation of the shaft.
Other objects, features and characteristics of the present invention, as well as the methods of operation and the functions of the related elements of the structure, the combination of parts and economics of manufacture will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification.